The present invention relates to improvements in cooling arrangements for vehicle engines and stationary engines.
Currently vehicle engines are cooled by pumping a liquid coolant around the engine block to pick up heat therefrom and to dissipate such heat from the coolant by passing same through a heat exchanger or radiator. Typically a mechanically driven coolant pump is provided which may be connected to or form part of the engine block and be driven directly from the engine itself by way of a belt and pulley drive. That is, when the engine is not operating the pump also is stationary and no coolant flow occurs other than by thermal syphoning effects. Conversely, when the engine is operating, the speed of rotation of the pump is directly related to the rotational speed of the engine. As a consequence of this, the volume flow rate of the coolant is also directly related to the rotational speed of the engine. This conventional arrangement is believed to have a number of disadvantages in practice including that while the engine is operating large volumes of coolant may be circulated by the pump even though the cooling requirements of the engine may not require same or cavitation may occur at high speeds restricting coolant flow. This also causes an energy drain on the engine and therefore a lack of engine efficiency. Also when the vehicle is stationary and idling, the engine speed is low providing a low coolant flow rate but a high flow rate at times is required. Similarly, each time gearing is changed (either manually or via an automatic transmission), there is instantly an inertia problem for the pump to vary the liquid flow rate immediately to accord with the changed engine speed. Finally, with modern vehicle engine design, there is a practical problem in that many accessories or moving parts of the engine are directly driven via a serpentine drive belt and associated pulleys from the engine drive shaft with the coolant liquid pump being one of these items. If the coolant pump did not have to be driven in this way, then it would, to some extent simplify the design of the drive for the other parts or devices. In addition, when a hot engine is turned off, the coolant continues to absorb heat from the engine block, which heat is slow to dissipate and which allows very high load temperatures, sometimes causing damage or needless wear.
The objective therefore of the present invention is to provide a novel coolant system for a vehicle engine that will overcome or minimise some or all of the aforementioned difficulties associated with the current mechanical drive arrangements.
Accordingly, the present invention provides a coolant system for a vehicle engine, said coolant system including a coolant flow circuit which in part includes passage means through an engine block of an internal combustion engine and through a heat exchanger, said coolant system further including a coolant pump means adapted, when operated, to cause coolant flow around said coolant flow circuit, said coolant pump means being driven by drive means independent from said engine. Conveniently said drive means may be an electric motor which may be either a single speed motor or a dual or variable speed motor. The drive means may be itself operated, to thereby drive the pump means, continuously while the engine is operated, or alternatively, the drive means may be thermally controlled in response to engine temperature whereby the pump means operates only when engine cooling is required. The pump means is preferably mounted in the lower heat exchanger (radiator) hose leading from the radiator to the engine block. It is, however, possible to locate the pump means in a number of different locations including the top radiator hose (leading from the engine block to the radiator), as part of the radiator either adjacent its inlet or its outlet, or connected to or as part of the engine block.
In accordance with a further aspect, the present invention provides a coolant system for an internal combustion engine, said coolant system including a coolant flow circuit for a coolant which in part includes passage means for the coolant through an engine block of the engine and through a heat exchanger, said coolant system further including a coolant pump means adapted, when operated, to cause coolant flow around said coolant flow circuit, said coolant pump means being driven by an electric motor independently of said engine, and a coolant temperature sensor means and controller means to control coolant flow delivery output from said coolant pump in response to differing coolant temperature levels being sensed by said coolant temperature sensor means, said controller means being arranged to vary the speed of the electric motor by pulsing the voltage level supplied thereto, the voltage level being pulsed for at least a period of operation of the engine for a period xe2x80x9conxe2x80x9d and a period xe2x80x9coffxe2x80x9d wherein the period xe2x80x9conxe2x80x9d is at least one second, with a percentage of the voltage xe2x80x9conxe2x80x9d relative to the voltage xe2x80x9coffxe2x80x9d increasing in response to the coolant temperature level increasing as sensed by said coolant temperature sensor means. In this way, the speed of the electric motor is varied in response to said differing coolant temperature levels being sensed by said coolant temperature sensor means and as a result the flow rate of coolant is similarly varied.
In one embodiment, the controller means enables differing voltage levels to be supplied to said motor in response to differing coolant temperature levels being sensed by said coolant temperature sensor means.
In one embodiment, the voltage level is pulsed for a period on and a period off, with the percentage of voltage on or the magnitude of the voltage on relative to voltage off periods increasing in response to sensed temperature level increases. Similarly the percentage of voltage on or the magnitude of the voltage on relative to the voltage off period may decrease in response to sensed temperature level decreases. Alternatively, a microprocessor may be used for infinitely varying voltage, on the size of pulsed voltage, in response to sensed temperature levels. In another embodiment, the voltage level is simply stepped from a minimum viable level to a maximum level in response to increased coolant sensed temperature levels. In a still further embodiment, a combination of the aforesaid pulsing of voltage and stepped increase of voltage levels might be used. Of course, voltage levels or the relative degree/percentage of voltage pulsing on to off will decrease in response to decreases in coolant sensed temperature levels.
Further preferred features and aspects of the present invention may be seen from the annexed patent claims which are hereby made part of this specification.